Generally, bumpers are mounted on front and rear sides of a vehicle to absorb the impact from collisions with other vehicles and objects. Bumpers act to decrease vehicle damage and minimize injury to persons inside the vehicle.
The bumper comprises a bumper beam mounted on the front and rear sides of the vehicle in a direction along a width of the same, an impact absorbing member provided on a front side of the bumper beam, and a bumper cover covering both the bumper beam and impact absorbing member to aesthetically conceal and protect the same.
The present invention relates to the apparatus and method for manufacturing the bumper beam. Conventionally, a bumper beam, when seen at a cross-section, includes a main body which is formed having a "W" shape with the two openings facing the vehicle, and a plate welded over the two openings such that two semi-circular tubes are formed in the bumper beam.
However, the manufacture of such a prior art bumper beam has drawbacks in that because two separate steps are needed--forming the main body and welding the plate to the main body--the process is complicated and time consuming. This ultimately acts to increase the overall manufacturing costs of the vehicle. In addition, as the plates used to cover the two openings are made through a pressing operation, much scrap is generated in forming the plates. Finally, a rim for welding the plates must be formed on the main body, further complicating the manufacturing process and increasing the overall weight of the vehicle.
To remedy these problems, a roll-forming process has come to be used in recent times in which a steel strip is roll-formed into a tubular cross section by a single roll-forming process. An example of such a manufacturing method is disclosed in U.S. Pat. No. 5,395,036 to Peter Sturrus et al.
However, in the above method, before forming each wall of a bumper beam, pre-operation for preparing a steel sheet having a web is needed so that the manufacturing process is complicated and the apparatus takes large space. Furthermore, the front wall is formed by welding both side edges of the steel sheet to each other so that the impact resistance reduces.